JPH1133888A - Mirror finished surface chamfering device for wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make mirror finishing of chamfered parts from both the front surface and rear surface without inverting the wafer. SOLUTION: A wafer W whose chamfered parts are to be subjected to mirror finishing is sucked in horizontal attitude by a vacuum chuck 31 of a wafer support 30. A polishing drum 30 to make mirror finishing of each chamfered part is borne in such a way as rotatable and also movable in the axial direction by a drum support 20 whose inclination angle is changeable centering on the revolving shaft C. A weight 37 is coupled with one side of the wafer support 30, and by this weight 37 a polishing pressure is generated to press the chamfered part of the wafer W to the peripheral surface of the polishing drum 10. The wafer support 30 is moved along a guide member 35, whereby the contact angle θ of the drum 10 relative to the chamfered part varies continuously or steppedly during the mirror finishing, and the chamfered part is made mirror finishing both from the front surface and rear surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for mirror-polishing a chamfered portion of a wafer uniformly.

[0002]

2. Description of the Related Art An edge portion of a semiconductor wafer such as a Si wafer is chamfered by grinding using a diamond grindstone in order to prevent chipping of the edge and crown during epitaxial growth. The chamfered edge portion includes problems such as processing distortion, damage due to impact, and dust generation, which cause crystal defects. Then, after chamfering the edge part by grinding, the chamfered part is mirror-polished. Japanese Patent Application Laid-Open No. 7-314304 discloses a device for rotating a drum on which a polishing cloth is mounted and pressing the outer peripheral portion of the wafer against the drum as mirror polishing of a chamfered portion. This apparatus includes three types of polishing drums: a polishing drum for polishing a chamfered portion of a wafer from the front side, a polishing drum for polishing from the back side, and a polishing drum for polishing from the peripheral end side. However, since a plurality of polishing drums are required to polish the chamfered portion of one wafer, the entire apparatus becomes large. Further, since the angle of each polishing drum with respect to the chamfered portion of the wafer is fixed, the chamfered portion cannot be polished into an arc-shaped cross section.

Therefore, a method has been implemented in which the chamfered portion of a wafer is polished from the front side and the back side with one polishing drum, utilizing the fact that the polishing cloth of the polishing drum is compressible. In this method, as shown in FIG. 1, a wafer 2 held by a chuck 1 is applied to a peripheral surface of a polishing drum 3 at a predetermined angle, and a chamfered portion of the wafer 2 is polished from the front side.
The wafer 2 is turned over and placed on another chuck 4, and the chamfered portion of the wafer 2 is polished from the back side. The wafer 2 whose chamfer is to be polished is pressed against the peripheral surface of the polishing drum 3 as shown in FIG. The force pressing the wafer 2 acts as a polishing pressure, but also causes the compressible polishing pad 5 to be dented. That is, wafer 2
Since the polishing cloth 5 is depressed following the contour of the chamfered portion, the chamfered portion of the wafer 2 can be polished by polishing twice from the front side and the back side.

[0004]

However, when the chamfered portion of the wafer 2 is polished by this method, the shape of the chamfered portion tends to be broken as the polishing amount increases. For example, as shown in FIG. 3, when the chamfered portion having the end face thickness x is mirror-polished, the end face thickness y decreases according to the polishing amount. If the end face thickness y is too small, the periphery of the wafer 2 may be chipped by a slight external force. Also in the case of surface polishing or the like, it becomes difficult to hold the wafer 2 with the carrier, and the wafer 2 may jump out of the carrier and become unpolished. In addition, since the chamfered portion of the wafer 2 is polished twice from the front side and the back side, various chamfered shapes such as arc-shaped cross sections cannot be handled. Furthermore, when the polishing process is switched from the front side to the back side, the wafer 2 needs to be turned over, which complicates the entire apparatus. The present invention has been devised in order to solve such a problem, and the shape of the chamfered portion is broken by changing the angle of the polishing drum in contact with the chamfered portion of the wafer with a simple equipment configuration. The purpose is to polish without.

[0005]

In order to achieve the object, a mirror chamfering apparatus of the present invention has a wafer support provided with a vacuum chuck for holding a wafer whose chamfer is mirror-polished in a horizontal state, A polishing drum arranged to be in contact with the chamfer, a drum support supporting the polishing drum rotatably and movably in an axial direction, and having a tilt angle that can be changed about a pivot axis; And a weight for pressing the chamfered portion of the wafer against the peripheral surface of the polishing drum to generate polishing pressure, and a horizontal guide member serving as a guide when the wafer support moves horizontally by the rotating polishing drum. Wherein the contact angle of the polishing drum with respect to the chamfered portion of the wafer changes continuously or stepwise during mirror polishing.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a mirror chamfering apparatus according to the present invention, a polishing drum 10 is disposed on a drum support 20, as shown in FIG. The drum support 20 is provided with a rotation drive motor 11 for rotating the polishing drum 10, and is provided so as to be tiltable around a rotation axis C so that the tilt angle θ can be adjusted. The drum support 20 is provided with a feed screw 22 that is pitch-fed by a forward / reverse motor 21, and the rotation of the feed screw 22 causes the polishing drum 10 to move forward and backward in the axial direction. The drum support 20 is turned by an electric motor (not shown) having an output shaft that is power-connected to the turning shaft C, and the polishing drum 10 is pressed against the wafer W at a predetermined angle. The turning of the drum support 20 may be either continuous or intermittent turning, and switching between continuous turning and intermittent turning is optionally controlled by an electric motor.

A wafer W to be mirror-chamfered is held on a vacuum chuck 3 rotatably provided on a wafer support 30.
The back surface is fixed to 1. The vacuum chuck 31 includes a rotation driving motor 32 provided on the wafer support 30.
It rotates with power from. A guide member 35 whose both ends are supported by the upright support portion 34 of the support base 33 is fitted into the wafer support 30. As the guide member 35,
For example, a mechanism such as an air slide with very small friction is used. A reel 36 is provided on one side of the wafer support 30.
Is suspended by a wire 38. The rightward force in FIG. 4 is applied to the wafer support 30 by the load of the weight 37. The wafer support 30 moves either rightward or leftward depending on the relationship between the force of the drum support 20 rotating clockwise and the load on the weight 37.

The wafer W to be subjected to mirror chamfering is
In FIG. 4, the chamfered portion is mirror-polished while moving rightward or leftward. When the mirror support is chamfered while moving the wafer support 30 to the right, first, the vacuum chuck 31 is used.
Is moved to the left end of the guide member 35, and the wafer W is positioned on the vacuum chuck 31 (a). After the wafer W is set, when the force of the motor 39 that pulls the wafer support 30 to the left is removed, the wafer support 30 becomes free and the weight 37
To move rightward (b). The wafer support 30 moved to the right hits the polishing drum 10,
The weight of the weight 36 pulling the wafer support 30 is the polishing pressure. The polishing pressure is adjusted by changing the amount of the weight 36. At this time, the upper surface of the chamfered portion of the wafer W is first polished by the polishing drum 10,
The tilt angle θ of the drum support 20 is adjusted.

The inclination angle θ of the polishing drum 10 is changed by rotating the drum support 20 around the rotation axis C according to a preset program. The change in the inclination angle θ may be either continuous A or intermittent B as shown in FIG. The program for changing the inclination angle θ is appropriately selected according to the chamfered shape. When the contact area between the polishing drum 10 and the wafer W is different depending on the inclination angle θ, the polishing pressure is not constant, and the polishing speed may be different. In such a case, in order to keep the polishing amount constant, it is also possible to control the inclination speed or residence time of the polishing drum as shown by the curve C. Conversely, it is also possible to set the inclination angle θ so as to increase the polishing amount.

In the case where the inclination angle θ is changed stepwise so as to change from the mirror polishing (a) of the upper surface of the chamfer to the mirror polishing (c) of the lower surface of the chamfer through the polishing (b) of the side surface of the chamfer, According to the state of contact between the polishing drums 10 _s , 10 _m , and 10 _f and the chamfered portion of the wafer W, the chamfered portion is as shown in FIG.
Is mirror-polished to the shape shown in FIG. Further, when the mirror processing is performed while the inclination angle θ is continuously changed, the chamfered portion of the wafer W is polished to a rounded shape. Further, during the polishing process, the polishing drum 10 is
Is moved in the axial direction to change the contact position with the wafer W, thereby preventing uneven wear of the polishing pad.

The polishing process can be started from the back surface of the chamfered portion of the wafer W. In this case, the wafer support 30 is positioned at the left end of the guide member 35, and the polishing drum 10 is pressed against the wafer W sucked by the vacuum chuck 31 (FIG. 4D), and the drum support 20 is moved counterclockwise. While rotating (d → c → b in FIG. 4), the chamfered portion of the wafer W is mirror-finished. As described above, since the chamfered portion is mirror-polished while changing the inclination angle θ of the drum support 20, the upper surface (front surface) to the lower surface (back surface) of the chamfered portion can be continuously polished. In this polishing step, the wafer W always moves in the left-right direction while being attracted to the vacuum chuck 31 of the wafer support 30 and does not need to be inverted. for that reason,
This is an apparatus suitable for mirror-beveling a wafer W, which is particularly large in diameter, without increasing the size of the equipment configuration.

[0012]

As described above, the mirror chamfering apparatus of the present invention performs mirror polishing of the chamfered portion while changing the contact angle of the polishing drum with respect to the chamfered portion of the wafer. The chamfered portion is mirror-finished from both front and back sides in a continuous operation without requiring a mechanism. In addition, since the wafer to be mirror-chamfered is always processed while being kept in a horizontal state, the influence of bending and the like is suppressed, and even a large-diameter wafer can be uniformly chamfered.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a conventional polishing of a chamfered portion with reversal of a wafer.

FIG. 2 is a view for explaining that a polishing cloth is depressed when a wafer is pressed against a polishing drum.

[Figure 3] Chamfer before and after mirror finishing

FIG. 4 is a diagram for sequentially explaining a process of mirror-finishing a chamfered portion of a wafer using a mirror-chamfering apparatus according to the present invention.

FIG. 5 is a graph showing the inclination angle of a drum support changed during polishing.

FIG. 6 is a diagram showing a positional relationship between a chamfered portion of a wafer mirror-polished from both sides and a polishing drum.

[Explanation of symbols]

10: Polishing drum 11: Motor for rotating and driving the polishing drum 20: Drum support 21: Motor for moving forward and backward 2
2: Lead screw 30: Wafer support 31: Vacuum chuck 3
2: Rotary drive motor 33: Support base 34: Standing support 35: Guide member 36: Reel 37: Weight 38: Wire 39: Motor W: Wafer C: Revolving axis θ: Dilution angle of drum support 10 _s : Mirror surface Polishing drum at the start of polishing 10 _m : Polishing drum during mirror polishing 10 _f : Polishing drum at the end of mirror polishing

Claims (1)

[Claims] 1. A wafer support provided with a vacuum chuck for horizontally holding a wafer whose chamfer is to be mirror-polished, a polishing drum arranged to be in contact with the chamfer of the wafer, and rotating the polishing drum. A drum support that is supported movably and axially movably and whose inclination angle can be changed about the rotation axis, and is connected to one side of the wafer support, and the chamfered portion of the wafer is pressed against the peripheral surface of the polishing drum for polishing. A weight for generating pressure, and a horizontal guide member for guiding the wafer support when the wafer support is horizontally moved by the rotating polishing drum, the contact angle of the polishing drum with respect to the chamfered portion of the wafer is continuous during mirror polishing. Or, a mirror chamfering device for a wafer characterized by changing stepwise.